Fertilization and early embryology: The influence of Vero cell culture on human embryo development and chorionic gonadotrophin production in vitro

Co-culture of human embryos with cell layers has generally shown that blastocyst formation rates are improved compared to routine culture in medium alone. In order to assess this further, we have additionally classified resulting blastocysts according to their morphology and secretion of human chorionic gonadotrophin (HCG). A total of 70 supernumerary human embryos from 15 patients were divided equally and randomly between two culture conditions: (i) co-culture with Vero cells ; and (ii) culture in our routine medium. Embryo development and morphology were recorded for up to 14 days in culture. The results showed that embryos on Vero cells had a significantly higher blastocyst formation rate (P <0.02) by or on day 6 of development than those in routine culture medium alone (77 and 46% respectively). For HCG analysis, the culture medium was changed in both culture systems on days 5, 7, 9, 12 and 14 of embryo development and analysed. Most embryos began to produce HCG between days 7 and 9, with HCG secretion being significantly higher from embryos on Vero cells between days 9 and 12 than from embryos in routine culture (P <0.03). The morphology of the blastocysts obtained was related to their ability to hatch and produce HCG but was not significantly better for one type of culture system than for the other.